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Würth Engine Sealing Compound, Silicone Special 250

Würth Engine Sealing Compound, Silicone Special 250

0890321

23 in stock

Key Features

  • Permanently elastic, acetate-curing silicone sealant for engine, transmission, and bodywork applications subject to extreme temperatures and vibration.
  • Withstands continuous temperatures up to 250°C and brief thermal peaks up to 300°C without loss of sealing integrity.
  • Cold-vulcanising silicone rubber - cures at room temperature to form a flexible, resilient seal.
  • Bridges large surface irregularities and maintains a reliable seal even after long-term exposure to vibration and mechanical stress.
  • Excellent adhesion and chemical resistance, suitable for contact with oils, coolants, and automotive fluids.
  • Does not run, sag, or pull threads, allowing clean application and precise bead control.
  • Fast skin formation within 6-12 minutes; full vulcanisation rate approximately 1.5mm per day.
  • High flexibility with up to 25% continuous movement absorption below 150°C.
  • Temperature resistant from -50°C to 250°C, short-term up to 300°C.
  • Ideal for high-heat engine components and metal joints requiring flexibility and chemical durability.
£13.99 GBP
£13.99 GBP
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Taxes included. Shipping calculated at checkout.

Shipping Information

What Are My Shipping Options?

In-Store Pickup

In-Store pickup is available on all purchase. Pickups are available Monday - Friday between the hours of 9:00–17:00. 

An email confirmation will be sent when your order is ready for collection. 

Free Shipping

We offer free Standard (2-3 Days) shipping on orders within the United Kingdom on orders over £100. Please note, some large items that require specialist courier companies, such as large mirrors and palleted items are excluded from this deal.

Shipping Fees

We also offer shipping at the following rates:

Standard-Size Parcel

Standard (UK Only) - 2-3 Days - £2.99

Express (UK Only) - 1-2 Days - £4.99

International (EU) - 3-7 Days - £14.99

International (ROW) - 5-10+ Days -£23.99


Large Parcel

Standard (UK Only) - 2-3 Days - £2.99

Express (UK Only) - 1-2 Days - £4.99

International (EU) - 3-7 Days - £14.99

International (ROW) - 5-10+ Days - £69.99

Most UK orders will be sent using Royal Mail, with larger items being sent with DPD.

International orders within the EU will normally be dispatched with Royal Mail, DPD, or UPS.

International orders to the rest of the world will normally be sent with DPD or UPS.

Please note, international delivery charges are very volatile and subject to change. We will do everything in our power to honour the delivery fee, however, in some cases, shipping may increase in price. In this event, you will be given the offer to pay the difference or cancel the order and receive a full refund.

Please note, we may be subject to various rules and restrictions in relation to some international deliveries, and you may be subject to additional taxes and duties over which we have no control. If such cases apply, you are responsible for complying with the laws applicable to the country where you live and will be responsible for any such additional costs or taxes.

Dispatch Times

Orders placed before 15:00 Monday - Friday will be shipped on the same day. 

Orders placed after this time will be shipped on the following business day,

Please note, we are closed at weekends, as well as English Bank Holidays.

Returns Policy

Our refund policy can be found at the following address: https://esupplyline.com/policies/refund-policy.

Further Information

You can contact us for further information on our shipping policies using the following:

Phone: 01953 711 881

Email: sales@esupplyline.com

Live Chat: Available on our website, Monday - Friday, 8:30 - 17:00.

Contact Form: https://esupplyline.com/pages/contact

View full details
Product Product subtotal Quantity Price Product subtotal
Würth Engine Sealing Compound, Silicone Special 250
Würth Engine Sealing Compound, Silicone Special 2500890321
Würth Engine Sealing Compound, Silicone Special 2500890321
£13.99/ea 		£0.00
£13.99/ea £0.00

Description

High-Temperature, Permanently Elastic Silicone Sealant

Würth Engine Sealing Compound Silicone Special 250 is a professional-grade, acetate-curing silicone sealant designed for use in automotive, industrial, and bodywork applications where components are exposed to high temperatures, vibration, and chemical stress. It forms a cold-vulcanised, permanently elastic silicone rubber seal that provides reliable performance across a wide range of materials and environments.

Outstanding Temperature and Chemical Resistance

This sealant is formulated to withstand continuous exposure to heat up to 250°C , with short-term peaks up to 300°C, making it ideal for sealing engine and transmission housings, crankcases, oil pans, and cylinder head covers. It resists degradation from engine oils, coolants, lubricants, and fuels, ensuring long-lasting sealing under harsh operating conditions.

Cold-Vulcanising, Non-Sagging Formula

The product cures at room temperature into a flexible, elastic silicone rubber that bridges surface imperfections and unevenness. Its non-sagging consistency prevents the material from running or forming threads during application, ensuring precise, clean bead lines even on vertical or overhead surfaces.

Flexible and Vibration-Resistant

Once cured, Würth Silicone Special 250 maintains permanent elasticity with 25% movement absoption (below 150°C) and 18% at higher temperatures. This elasticity allows it to absorb vibrations and thermal expansion differences between materials, preventing cracking or separation over time.

Fast Skin Formation and Efficient Curing

The silicone begins to form a skin within 6-12 minutes, depending on humidity and temperature, and cures at approximately 1.5 mm per day. This allows quick assembly and minimal downtime in production or repair environments.

Versatile Application Range

Suitable for use in a wide variety of sealing and bonding applications across engines, mechanical systems, and bodywork, including:

  • Cylinder heads, crankcases, oil pans, and gear housings.
  • Radiators, differentials, and transmission covers.
  • Lighting housings, indicator assemblies, weld seams, and joints.

More Information

Application Instructions

  1. Ensure all surfaces are clean, dry, and free from oil, grease, and dust.
  2. Cut the cartridge nozzle to the desired bead width.
  3. Apply a continuous bead of sealant to one surface using a suitable applicator or cartridge gun.
  4. Assemble the components before skin formation (within approximately 6-12 minutes).
  5. Allow to cure at room temperature; curing rate is approx. 1.5 mm/day at 23°C and 50% relative humidity.
  6. Avoid excessive joint movement until the sealant is fully vulcanised.

Usage Notes

  • Processing temperature: 5°C to 40°C.
  • Temperature resistance: -50°C to 250°C (short term up to 300°C).
  • Store in a cool, dry area below 25°C.
  • Shelf life 18 months from production.
  • Ensure adequate air circulation during curing.

Specifications

Chemical Basis: Acetate-curing silicone

Colour: Red

Contents: 70 ml (73 g weight)

Density: 1.05 g/cm³ (at 20 °C)

Odour: Vinegar-like (acetic acid)

Skin Formation Time: 6–12 min (at 23 °C, 50% RH)

Curing Rate: Approx. 1.5 mm/day (at 23 °C, 50% RH)

Shore A Hardness: 30

Elongation at Break: 300 %

Continuous Movement Absorption:

• Up to 150 °C: 25 %

• Above 150 °C: 18 %

Temperature Resistance: -50 °C to +250 °C (short-term +300 °C)

Processing Temperature: +5 °C to +40 °C

Adhesion: Excellent on metals, glass, ceramics, and coated surfaces

Curing Mechanism: Acetoxy (acidic) curing system

Shelf Life: 18 months (cool, dry storage below 25 °C)

Corrosion Protection: Yes (non-corrosive to metals when cured)

Elasticity: Permanently elastic

Paint Compatibility: Not overpaintable

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